CODEWITHSUNDEEP
javascript
Prem
Prem

Reputation: 5997

How to use conditional(ternary) operator in javascript

Given a string, I need to get the number of occurrence of each character in the string.

Input : "Hello world" 
Expected Output : { H: 1, e: 1, l: 3, o: 2, ' ': 1, w: 1, r: 1, d: 1 }

When I use if else condition the logic works fine , but not with ternary operator.

const string = "Hello world";
const chars = {};

for(let char of string) {
    if(!chars[char]) chars[char] = 1;
    else chars[char]++;
}
console.log(chars); // { H: 1, e: 1, l: 3, o: 2, ' ': 1, w: 1, r: 1, d: 1 }


But, When I replace the if else condition with ternary operator, the output is unexpected 

chars[char] = !chars[char] ? 1: chars[char]++
console.log(chars); // { H: 1, e: 1, l: 1, o: 1, ' ': 1, w: 1, r: 1, d: 1 }

Upvotes: 1

Views: 787

Answers (2)

Jonathan Lonowski
Jonathan Lonowski

Reputation: 123553

In this case, you'll want to move the ++ before chars[char]:

chars[char] = !chars[char] ? 1 : ++chars[char]

Or just an addition:

chars[char] = !chars[char] ? 1 : chars[char] + 1

Or, even shorter:

chars[char] = (chars[char] || 0) + 1

Whether you place the ++ before or after a value changes the value it returns:

  • After (chars[char]++), the operator will return the original value, 1, as it increments to 2. The assignment operator, then, will receive the 1 and place it back into chars[char], undoing the increment.

  • Before (++chars[char]), the operator will return the modified value, 2, for the assignment to use. Here, the operators aren't in conflict with each other, as they're both setting the same value.

Upvotes: 3

paul
paul

Reputation: 22011

You are setting chars[char] to the result of chars[char]++ which is 0

You want: chars[char] = !chars[char] ? 1: chars[char]+1

Upvotes: 1

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